20-cent Airplane National Postal Museum

Aviation US Back of Book Air Mail 20 Cent Denomination Stamps for sale

China Clipper - Wikipedia

Tours and Itineraries National Postal Museum

U.S. Parcel Post stamps of 1912–13 - Wikipedia

The Airplanes National Postal Museum

National Postal Museum - Wikipedia

Air Stamps–Heavier than Air: Biplanes, Monoplanes, Jets & Helicopters

How the Inverted Jenny, a 24-Cent Stamp, Came to Be Worth a Fortune, At the Smithsonian

Chronology: 1980-1989 Air & Space Forces Magazine

Pictorial Issues (1869-1870)

The Postal Airplanes National Postal Museum

Museum's F-16XL returns home - Aerotech News - Edwards AFB